System for use with storage tanks for receiving, delivering or retaining liquified gas

ABSTRACT

A system for filling and draining a storage tank with liquified gas and/or for cooling and heating stored liquified gas includes a heat exchanger having a chamber with two nests of tubes, one for circulating cooling or heating medium and the other for circulating liquified gas. The other nest of tubes is connected by conduit means to a storage tank while the chamber itself is connected by further conduit means both with the first conduit means and also through a compressor and pump with the storage tank.

United States Patent n91 Kober [111 3,809,153 [45] May 7,1974

[ SYSTEM FOR USE WITH STORAGE TANKS FOR RECEIVING, DELIVERING OR RETAINING LIQUIFIEI) GAS Inventor: Drago Kober, Rondorf/Cologne,

Germany Assignee: Liquid Gas Anlagen Union GmbH,

Remagen-Rolandseck, Germany Filed: Oct. 1, 1971 Appl. No: 185,617 1 [30] Foreign Application Priority Data Oct. 1, 1970 Germany 2048271 US. Cl. 165/62, 62/45 Int. Cl. F25b 13/00 Field of Search 165/61, 62, 63, 26, 27;

[56] References Cited UNITED STATES PATENTS 3,205,665 9/1965 Vanl'lorn 62/45 Primary Examiner -Charles Sukalo Attorney, Agent, or Firm-Markva & Smith 7 ABSTRACT A system for filling and draining a storage tank with liquified gas and/or for cooling and heating stored liquified gas includes a heat exchanger having a chamber with two nests of tubes, one for circulating cooling or heating medium and the other for circulating liquified gas. The other nest of tubes is connected by conduit means to a storage tank while the chamber itself is connected by further conduit means both with the first conduit means and also through a compressor and pump with the storage tank.

9 Claims, 9 Drawing Figures PATENTEMY 71914 I 3809;153-

- SHIN 5 UF 6 1 SYSTEM FOR USE WITH STORAGE TANKS FOR RECEIVING, DELIVERING OR RETAINING LIQUIFIED GAS The invention relates to an arrangement for filling and draining storage tanks with liquified gas and/or for cooling or heating the stored liquified gas. The arrangement is particularly useful for tanks on ships.

It is known that, for carrying out technical refrigeration processes, a liquified gas plant is used which contains heat exchangers of different types in addition to the liquified gas pumps and compressors. Hence, acondenser cooled by water or sea water is inter alia necessary in order to condense, in a reliquefaction circuit, vapours which are formed during the charging of liquified tanks or as a result of warming of the liquified gas. By this means, an impermissibly high pressure in the liquified gas tank is avoided and also simultaneously a coolingof the loaded material is produced. With the unloading of the tank, Vaporizers are necessary in order to be able to produce gas from the liquid, which gas is delivered with the aid of a compressor as a pressurecushioning'means to the tank to be discharged. This produces a sufficiently large initial pressure for'the discharge pumps. Furthermore, the necessity also arises from time to time for the liquid to be heated before loading or unloading, for which purpose a heat exchanger is likewise necessary. The liquified gas plant thus requires three heat exchangers, in order to be able to accommodate all requirements for loading and unloading the storage tanksand also for cooling or heating of the loaded material. Since each such apparatus has to be provided in duplicate for safety reasons, the number of heat exchangers which must be present is thus doubled.

It is an object of this invention to reduce and to simplify the apparatus required for use with tanks which receive, deliver or contain liquified gas.

ln accordance with the invention two nests of tubes which are independent of one another areassociated with a chamber of the heat exchanger, one of the nests of tubes being on top and arranged such that it can be charged with liquified gas and the other nest of tubes being at the bottom and arranged to be charged with water, for example, fresh water or sea water. The chamber of the heat exchanger is provided in the upper part with a gas inlet and a gas outlet connected through the compressor to the storage tank and the lower part of the heat exchanger is connected to the inlet pipe for feeding liquified gas to the tank.

' By such a construction, a heat exchanger'which can be utilized for all necessary purposes is obtained. The heat exchanger can be used as a condenser or evaporator and also as a liquid heater with an evaporator and condenser function. Using a single heat exchanger, it is possible to carry out all processes which can arise when loading or unloading a liquified gas tank, and also when heating or cooling the loaded material. At the same time, the construction of the system is simplified. In ad dition, a substantial saving in space is obtained withthe arrangement. No longer is it necessary to have three different heat exchangers, or six, because of safety regulations, but a single or pair of heat exchangers is sufficient for meeting all contingencies.

The liquid level in the heat exchanger chamber can be regulated in relation to the nests of tubes by means of a level regulator known in the art. In some instances a level at which the two nests of tubes areimmersed in the liquid will be required while in other instances the height will be adjusted between the two nests of tubes. Level-controlled injection valves are advantageously arranged in the pipes which lead to the bottom side of the heat exchanger. The invention is more fully explained by reference to the examples shown in the drawing.

FIG. 1 shows diagrammatically the construction and arrangement of the system according to the invention With the operating arrangement for carrying out refrigeration processes in a liquified gas plant, there is provided a heat exchanger 1, in which the chamber 1 is equipped with two nests of tubes 2 and 3 which are independent of one another. The bottom nest of tubes 2is connected to the pipes 14, 15 for circulating water, which water can be fresh water or sea water, which may be heated by other power units, for example, main engines or auxiliary engines which are on board a ship. The loaded material in liquified form fiowsthrough the nest of tubes 3 situated above the nest 2 which is connected by means of the pipes 17 and 18 to the liquified gas tank 10. Provided on the upper sideof the chamber 1' of the heat exchanger 1 is a connection 4 for a gas inlet and a connection 5 for a gas outlet. From these connections 4 and 5, pipes 19 and 20 lead to a com pressor 11. The compressor communicates with the tank 10 through the pipe 23 and the branch pipes 21 and 22. Provided on the underside of the chamber 1' of the heat exchanger 1 are connections 6 and 7 for liquified gas, the connection .6 communicating via the pipe 24 with the pipe 17 and the connection 7 via the pipe 25 with the pipe 18. Arranged in the pipes 24 and 25 are regulating valves 8 and 9, which can be operated by a pressure medium, for example, pneumatically. By means of a level regulator (not shown), the liquid in the chamber 1' of the heat exchanger 1 can be maintained at the height necessary for the particular function of the heat exchanger.

Apump 12 for drawing liquified gas from tank 10 can be connected via the pipe 26 to the pipe 17 or 18, and a pipe 28 extends'frorn the pipe 18 to a connection point 16 for feeding and dispensing liquified gas to and from the system. Represented at 13 is a spray pipe, which is in the tank 10 and is connected by pipe 29 with pipe 17 or pipe 18. Shut-off valves 30 are arranged at predetermined positions in the pipes to control the direction of flow therethrough.

As shown in FIG. 1, the entire system is duplicated, to meet safety regulations, and suitable connecting pipes are provided, so that it is possible for one or the other of the systems to be brought into use at will. As regards the other system, the reference numerals for the corresponding parts are in each case provided with the addition a. Another tank 10a is also indicated, so

as to show that more than one tank can be connected to such a gas plant.

FIG. 1 shows the system with the part of the pipe arrangement in darker lines designating the flow pattern required for loading the tank 10, the heat exchanger 1 acting as a condenser. To avoid an impermissibly high pressure rise in the tank, gas which is formed with the spraying of the liquid loaded material through the pipes 28, 18 and 29 and through the spraying pipe 13 in the tank is drawn off through pipes 23 and 22 by suction from the compressor 11, compressed and fed to the chamber 1 in the exchanger 1 through pipe 19. The gas condenses on the lower nest of tubes 2, through which water, for example sea water, is flowing. The condensate is expanded to tank pressure and once again mixed with the charging flow in the pipe 29 by way of pipes 24 and 17.

For carrying out the discharge operation, illustrated in FIGS. 2 and 3, the heat exchanger 1 serving as a vaporizer is'used. In order to maintain an adequate preliminary pressure for the discharge pump 12, the gaseous load in this process is forced into the tank which is to be discharged. For this purpose, a component flow is branched off from the liquid discharge flow via the pipes 18 and 25-and is vaporized in the chamber 1' of the heat exchanger 1. Depending on the positioning of the valves in the piping system, the chamber 1 can in such a case be heated with coolant water by way of the nest of tubes 2 and the pipes 14 and 15 or with the liquified gas. In this case (FIG. 3), the liquified gas to be discharged, after leaving the tank 10, is conveyed through the upper nest of tubes 3 of the heat exchanger 1 by means of pipes 17, 18 and the liquid to be vaporized is withdrawn from the main flow 18 downstream of the heat exchanger through pipe 25.

When loading and with simultaneous heating of the load (FIG. 4), the heat exchanger 1 serves as a liquid heater. When loading liquified gas containers consisting of steel which cannot withstand low temperatures, the material being loaded must be heated to a higher temperature before entering the tank 10. For this purpose, the liquified gas is conducted beforehand through the upper nest of tubes 3 of the heat exchanger 1. Water, for example sea water, flows through the lower nest of tubes 2. In this case, the chamber 1 is approximately half filled with liquified gas, i.e. up to the level 31, it being possible to adjust this level by a level regulator. The water flowing through the nest of tubes 2 causes vaporization of the liquified gas in the chamber 1, the ascending vapour-condensing on the nest of tubes 3 through which the cold load is flowing in the upper part of the heat exchanger 1 and drips back again to condensate. The vaporization heat given off in such a case serves to heat up the material forming the load.

When discharging with simultaneous heating up of the material forming the load (FIG. 5), the heat exchanger 1 serves as a liquified heater/vaporizer. The liquid gas to be heated up is conducted through pipe 17 to the upper nest of tubes 3 of the heat exchanger 1. The liquified gas then flows towards the outlet 16 through pipe 18 with a portion being diverted through pipe 25 and being supplied for vaporization purposes to the chamber 1. The necessary heat for vaporization is extracted from the water, for example sea water, flowing through the lower nest of tubes 2. Using this process, the vapour ascending in the chamber 1 will also condense on the upper nest of tubes 3, thereby giving off its heat of condensation to the liquified gas to be heated up in the nest of tubes and dripping back again. Some of the gas vaporized in the boiler chamber is however drawn off through pipe 20 by suction from the compressor 1 l, compressed and forced-into the tank 10 which is. to be discharged, in order to assure a sufficient preliminary pressure for the discharge pump- 12.

To cool the load while it is being transported (FIG. 6), the heat exchanger 1 serves as a condenser, the cooling of the load being effected by reliquefaction of the gaseous load, and this can for example be carried out while the ship is under way. Gas is withdrawn by suction from the tank 10 through pipes 23 and 22 compressed in the compressor 11 and forced through pipe 19 into the chamber 1 of the exchanger 1, where it condenses on the lower nest of tubes 2, through which water, for example sea water, is flowing. The condensate is expanded to tank pressure and again supplied to the tank 10 through the pipes 25, 18, 29. In order to obtain a thorough mixing in the tank, the liquified gas in the tank can at the same time be constantly circulated by means of the pump 12.

For heating the load while it is being transported, the heat exchanger 1 serves asa liquid heater (FIG. 7), it being possible for the load to be heated, for example, while the ship is under way. For this purpose, the liquified gas is pumped through the upper nest of tubes 3 of the heat exchanger 1 by means of the pump 12 and via the pipe 17. In this case, the heat necessary for the heating operation is extracted from the steam condensing on the upper nest of tubes 3. The heated load flows back through the pipes 18 and 29 into the tank 10. The chamber 1' of the heat exchanger 1 is once again approximately half filled to the level 31 with liquified gas. The water flowing through the lower nest of tubes 2 supplies the necessary heat for vaporization.

By the arrangement of the two nests of tubes at different heights in the heat exchanger 1, namely, the upper nest for liquified gas and the lower nest for water, it is possible for the same heat exchanger to be utilized as both a vaporizer and a condenser.

In the case where a load is to be cooled, which is not suitable as a refrigerating agent, for example, acetaldehyde or butadiene, or when the load already tends to polymerise at temperatures which are reached in the compressor with the usual reliquefaction process, as for example vinyl chloride, a closed refrigeration cycle which is independent of the charging gas can be included by incorporating the heat exchanger of a second liquified gas plant (see FIG. 8). In this case, the chamber l' of the heat exchanger 1 is filled with a suitable refrigerant up to a level above the upper nest of tubes 3. Through the pipe 20, vaporized refrigerant is withdrawn by suction by the compressor 11 and forced through the pipes 33 and 19a into the chamber of the exchanger 1a. This refrigerant vapour condenses on the lower nest of tubes 2a, through which in this process coolant water, for example sea water, is flowing.

The refrigerant condensate is returned through pipes 25a, 32 and 25 to the chamber 1 of the exchanger 1. The heat necessary for vaporizing the refrigerant in the heat exchanger 1 is drawn off from the liquid load which is flowing through the upper nest of tubes 3 of the heat exchanger 1, whereby the contents of the tank can be cooled without reliquefaction.

In a manner similar to that of the cooling procedure I represented in FIG. 8 and comprising a closed refrigeration circuit, it is possible for a heating pump circuit shown in FIG. 9, incorporating the exchanger of the second liquified gas plant, to be connected for heating up loaded material which cannot be used as a refrigerant. With this procedure, the chamber of the exchanger 1a is filled with a suitable working medium for the heating pump circuit, which can be a conventional refrigerant up to a level which is above the lower nest of tubes 2a. By way of the pipe a, vaporized working medium is now drawn off by suction by the compressor 11a and forced through pipes 34 and 19 into the chamber 1' of the heat exchanger 1, where it condenses on the upper nest of tubes 3 through which the liquid loaded material is flowing, and thereafter flows back as condensate through the pipe 32 to the chamber of exchanger la and is again vaporized therein. The necessary heat for vaporization supplied by the sea water or fresh water flowing through the lower nest of tubes 2a. This vaporization heat, and also the superheating heat taken up in the compressor, are given ofi' in the heat exchanger 1 to heat the liquid loaded material flowing through the pipes 26, 17, 3, 18, 29 and 13.

I claim:

l. A system for filling and draining a storage tank with liquified gas and/or for cooling and heating stored liquified gas comprising a. a pump with means connecting its inlet with said storage tank for withdrawing liquified gas from said storage tank,

b. a compressor with means alternatively connecting its inlet or outlet with said storage tank for liquifying gas,

c. a heat exchanger for cooling or heating gas in gase ous or liquidform, said heat exchanger comprising means defining a chamber, a lower nest of tubes within said chamber for conveying a cooling or heating medium, an upper nest of tubes within said chamber positioned above said lower nest of tubes for conveying liquified gas, and inlet and outlet means at both the top and bottom of said chamber,

(1. first conduit means between the outlet of said pump, said upper nest of tubes and said inlet and outlet means at the bottom of said chamber, and valve means for controlling flow therebetween, and

e. second conduit means between said inlet and outlet means at the top of said chamber and the inlet and outlet of said compressor, and further valve means for controlling flow therebetween.

2. A system as defined in claim 1 wherein said first conduit means includes further conduit means for feed 6 ing liquified gas into and out of said system.

3. A system as defined in claim 1 wherein said first conduit means comprises a loop of pipe with the opposite ends thereof connected to the opposite ends of said upper nest of tubes, a pipe extending from said loop. to said storage tank and a further pipe extending from said loop to said pump.

4. A system as defined in claim 3 wherein said second conduit means comprises a pair of pipes extending from said inlet and outlet means at the bottom of said chamber and said loop of pipe.

5. A system as defined in claim 1 wherein said second conduit means comprises a pair ofpipes extending between said inlet and outlet'means respectively at the top of said chamber and the inlet and outlet of said compressor.

6. A system as defined in claim 1 further comprising means for adjustably controlling the level ofliquified gas in the chamber of said heat exchanger.

7. A system as defined in claim 6 further comprising regulating valves responsive to said adjustable level control for controlling the flow of liquified gas to and from said chamber through the inlet and outlet means at the bottom of said chamber. 7

8. A system as defined in claim 1 comprising a. a further heat exchanger for cooling or heating gas,

said further heat exchanger comprising means defining a chamber, a lower nest of tubes within said chamber for conveying a cooling or heating medium, an upper nest of tubes within said chamber positioned above said lower nest of tubes for conveying liquified gas, and inlet and outlet means at both the top and bottom of said chamber,

b. a further compressor,

c. third conduit means between said inlet and outlet means at the top of said further heat exchanger chamber and the inlet and outlet of said compressors and d. pipes extending between the outlets of both said compressors and between the outlet means at the bottom of both saidchambers of said heat exchangers respectively,

e. whereby a closed refrigeration circuit is provided independent of the loaded liquified gas.

9. A system as defined in claim 8 comprising a further pipe extending between the outlet of said further compressor and the inlet means at the top of the chamber of said first heat exchanger whereby a heat pumping circuit is provided which is independent of the charging gas for heating the loaded liquified gas. 

1. A system for filling and draining a storage tank with liquified gas and/or for cooling and heating stored liquified gas comprising a. a pump with means connecting its inlet with said storage tank for withdrawing liquified gas from said storage tank, b. a compressor with means alternatively connecting its inlet or outlet with said storage tank for liquifying gas, c. a heat exchanger for cooling or heating gas in gaseous or liquid form, said heat exchanger comprising means defining a chamber, a lower nest of tubes within said chamber for conveying a cooling or heating medium, an upper nest of tubes within said chamber positioned above said lower nest of tubes for conveying liquified gas, and inlet and outlet means at both the top and bottom of said chamber, d. first conduit means between the outlet of said pump, said upper nest of tubes and said inlet and outlet means at the bottom of said chamber, and valve means for controlling flow therebetween, and e. second conduit means between said inlet and outlet means at the top of said chamber and the inlet and outlet of said compressor, and further valve means for controlling flow therebetween.
 2. A system as defined in claim 1 wherein said first conduit means includes further conduit means for feeding liquified gas into and out of said system.
 3. A system as defined in claim 1 wherein said first conduit means comprises a loop of pipe with the opposite ends thereof connected to the opposite ends of said upper nest of tubes, a pipe extending from said loop to said storage tank and a further pipe extending from said loop to said pump.
 4. A system as defined in claim 3 wherein said second conduit means comprises a pair of pipes extending from said inlet and outlet means at the bottom of said chamber and said loop of pipe.
 5. A system as defined in claim 1 wherein said second conduit means comprises a pair of pipes extending between said inlet and outlet means respectively at the top of said chamber and the inlet and outlet of said compressor.
 6. A system as defined in claim 1 further comprising means for adjustably controlling the level of liquified gas in the chamber of said heat exchanger.
 7. A system as defined in claim 6 further comprising regulating valves responsive to said adjustable level control for controlling the flow of liquified gas to and from said chamber through the inlet and outlet means at the bottom of said chamber.
 8. A system as defined in claim 1 comprising a. a further heat exchanger for cooling or heating gas, said further heat exchanger comprising means defining a chamber, a lower nest of tubes within said chamber for conveying a cooling or heating medium, an upper nest of tubes within said chamber positioned above said lower nest of tubes for conveying liquified gas, and inlet and outlet means at both the top and bottom of said chamber, b. a further compressor, c. third conduit means between said inlet and outlet means at the top of said further heat exchanger chamber and the inlet and outlet of said compressors and d. pipes extending between the outlets of both said compressors and between the outlet means at the bottom of both said chambers of said heat exchangers respectively, e. whereby a closed refrigeration circuit is provided independent of the loaded liquified gas.
 9. A system as defined in claim 8 comprising a further pipe extending between the outlet of said further compressor and the inlet means at the top of the chamber of said first heat exchanger whereby a heat pumping circuit is provided which is independent of the charging gas for heating the loaded liquified gas. 